Processing sun-cured tobacco

ABSTRACT

A method of processing sun-cured tobacco, comprises harvesting a predetermined amount of whole tobacco plants, and curing the leaves on the whole tobacco plants by exposing them to sunlight, without separating the leaves from the stalk.

The present invention relates to a method of processing sun-cured tobacco and, in particular, relates to a method of harvesting sun-cured tobacco.

Sun-cured tobacco dries by exposure to sunlight, either under a curing structure that can be a transparent cover or by direct sunlight and is a process that is commonly used for curing certain tobacco types, especially oriental tobacco.

Oriental tobacco is primarily cultivated in Greece, Bulgaria, the Republic of Macedonia, and Turkey, but also in Egypt, South Africa, and elsewhere. Oriental tobacco is also known as Turkish tobacco and is a highly aromatic tobacco that has smaller leaves than other tobacco types and is the principal tobacco that can be sun-cured.

Other tobacco types are not suitable for sun-curing since this does not provide the final tobacco with the desired characteristics suitable for use in smoking articles. Instead, other tobacco types undergo different processing including air-curing, fire-curing, and flue-curing. Air curing involves hanging tobacco, notably Burley tobacco, in ventilated barns without subjecting it to sunlight and allowing it to dry over a period of four to eight weeks in order to provide a tobacco high in nicotine. Fire curing involves hanging the tobacco in barns without subjecting it to sunlight, maintaining a fire on continuous or intermittent low smoulder in the barn and allowing the tobacco to cure over a period of three days to ten weeks. Flue-curing involves hanging tobacco in curing barns that have flues from externally-fed fire boxes, and heat-curing the tobacco without exposing it to smoke or sunlight, whilst slowly raising the temperature over the course of the curing. The process generally takes about a week.

During the normal harvesting and curing cycle of sun-cured tobacco, the tobacco leaves are manually removed from the plants whilst the plants are in the field, so as to leave the stalks behind, and the leaves are then threaded onto a string to provide approximately 200 to 500 leaves per meter of string material. The string is then hung allowing the tobacco leaves to be sun-cured. The remaining stalk material is then removed separately. Thus, the harvesting and processing of sun-cured tobacco is extremely time consuming, as well being labor intensive.

It would be desirable to provide a more efficient method for processing sun-cured tobacco. It would also be desirable to provide a method for processing sun-cured tobacco that is economical. Furthermore, it would be desirable to provide an improved method for harvesting sun-cured tobacco.

Accordingly the present invention relates to harvesting the whole tobacco plant for sun-curing. This is different from conventional processing for sun-cured tobacco in which the leaf material is manually separated from the stalk material.

Harvesting the whole tobacco plant instead of separately removing leaves from the plant significantly reduces the duration of the process with the benefit that the risk of loss of tobacco products, due to adverse weather conditions during the harvesting cycle, is reduced.

Additionally, the labor cost associated with the harvesting cycle can be considerably reduced since it is easier for the workers to handle the whole harvested tobacco plant compared to separating individual leaf material.

In particular, it is much easier and less time consuming to attach or support the whole tobacco plant on a support material compared to the conventional process of stringing each leaf separately.

By “support material” it is meant a material to which the tobacco plant is attached or on which the tobacco plant is supported to allow it to be hung so that air can circulate through and around the tobacco plant. Suitable support materials include string, wire, rods, poles, sticks or any similar elongated material upon which the tobacco plant can be attached. Typically, attachment is carried out by threading or stringing the tobacco plant onto the support material.

Furthermore, the whole tobacco plant can be attached to or support by the support material by the stalk either manually or mechanically. This is in contrast to conventional process of stringing of loose tobacco leaves which is typically performed manually.

Additionally, since no stalk material will remain in the tobacco field after harvesting, the field can be immediately prepared for further tobacco cultivation.

The harvesting of the whole tobacco plant also provides advantages for processing steps that follow the harvest method. For instance, during the curing process of the whole oriental tobacco plants, air and sunlight are more evenly transmitted to the tobacco leaves. Therefore, the curing process consumes less time and reduces undesired variability in properties, such as moisture levels, between different leaves.

Accordingly, the present invention relates to a method of processing sun-cured tobacco, comprising harvesting a predetermined amount of whole tobacco plants, supporting the whole tobacco plant on a support material and sun-curing the leaves on the whole plant.

By harvesting the whole tobacco plant, it is meant that no stalks or leaves are intentionally left in the field, i.e. the entire plant with all leaves is harvested. Thereby, the leaves stay connected to the stems, and the stems stay connected to the stalk.

Preferably, about 20 to 50 whole tobacco plants are attached to each metre of support material.

The support material is typically attached to or supported on frame comprising vertical supports, such as posts or walls, to maintain the support material above the ground at a height at which the whole tobacco plant does not touch the ground when attached to or support on the support material. This allows air to circulate freely around each plant, which is important for avoiding the imbalance of certain leaves curing more than others.

The support material and the frame together are referred to herein as the “curing structure”.

The tobacco plants are preferably attached by the stalk end of the plant, such that when the support material is mounted onto the curing structure, the plants are upside-down, with the leaves being closer to the ground than the stalk end.

Preferably, dividers are provided on the support material between the whole tobacco plants, in order to keep a predetermined distance between each of the plants. This improves the curing of the tobacco leaves, as air can more easily circulate through and between the plants. Preferably, the curing structure is provided directly in or adjacent the tobacco fields where the tobacco plants are harvested.

The entire tobacco plants are preferably strung by hand or by mechanical stringing equipment, which facilitates preparation for the curing process.

For curing the tobacco leaves, it is preferable that the curing structure is permeable to air, such that air can flow through the hung plants in a uniform manner. Preferably, the curing structure is covered with a transparent cover, in order to prevent rain from falling onto the supported whole tobacco plants.

After curing and before bailing, the whole tobacco plants are preferably stored in an enclosed or covered structure having open sides. In order to be shipped, the cured whole tobacco plants are bailed, wherein each bail can comprise several layers of whole tobacco plants. Preferably, one layer comprising several whole tobacco plants is oriented in a first direction, and another layer below or above is oriented in the opposite direction. By layering the whole tobacco plants in such a way, the bail is more stable.

The whole tobacco plants are preferably forwarded to a leaf processing facility after curing. Typically, in this further processing the whole tobacco plants are threshed in threshing machines, in order to separate the cured tobacco leaf material from the stalk and stem material of the tobacco plant. By threshing the whole tobacco plants, it is not only possible to separate the leaves from the stalk of the plant, but also to separate the stem material from the leaf material. This enables to provide a very fine tobacco leaf material with high quality. The separated stalk and stem material can then be used for expanded tobacco material. Expanded tobacco can be prepared according to processes well known to the person skilled in the art.

In order to avoid the threshed oriental tobacco plants becoming too dry, which would make it unsuitable for use in many tobacco products, it is preferred that the cured tobacco plants are conditioned to increase their moisture content before being threshed in the leaf processing facility. As a result, the processed tobacco material will provide a better structure for a cigarette product. The moisture content of the whole oriental tobacco plants is preferably increased to at least 12% oven volatiles (o.v.) through the conditioning process.

The conditioning of the whole tobacco plants is preferably achieved by using steam, water, or a mixture of steam and water. The steam, water, or mixture thereof can be provided at the desired temperature, in order to achieve the preferred moisture degree for the tobacco plants.

After conditioning, the leaf material is preferably dried during a drying process. During drying, the moisture content of the tobacco leaf material is decreased to such a degree in order to constitute cut filler material for cigarettes. In addition, this provides a product that can be stored for a longer period.

In order to dry the conditioned leaf, the separated tobacco leaf material is preferably heated in a stream of hot air at a temperature of between 150° C. and 400° C., in order to dry the leaf material. In order to create cut filler material, the dried tobacco leaves are preferably further cut to a width of between 0.3 mm to 1.3 mm.

In an alternative process to bailing the whole tobacco plants and then threshing to separate the leaves, stems, and stalks, the cured leaves may be separated from the strung whole tobacco plants directly after the curing process. In this process, the cured tobacco leaves are preferably manually removed from the tobacco plant stalks while the whole tobacco plants are still hanging in the curing structure. As a result, after separating the cured tobacco leaves from the stalks, the stalk material will remain on the curing structure ready for further processing, as described above. The removal of the tobacco leaves is preferably achieved by cutting with a knife. Since the curing process reduces the moisture content of the leaves, this makes removal of the tobacco leaves easier than when the leaves are removed manually from the stalk in the tobacco field. Further, removal of the leaves from the hung tobacco plants enables the worker to operate standing up whereas conventional leaf removal occurs whilst the plant is still in the ground and requires the worker to kneel or bend down. This enables the harvester to work more efficiently.

The separated leaves can then be conditioned, cut and dried according to the processes described above.

A preferred embodiment of the present invention is shown by FIG. 1. FIG. 1 shows a method of processing tobacco according to the invention comprising process steps 1 to 8.

According to step 1, the whole oriental tobacco plant is harvested in the tobacco field.

In step 2, a predetermined amount of whole tobacco plant is then strung on a stringing material, such as a thread.

Next, during process step 3, the strung whole tobacco plant is supported on a frame to form a curing structure, and a transparent protective cover is placed over the curing structure. The plant is then left exposed to sunlight for a period of about ten to twenty days.

The cured whole oriental tobacco plant is then bailed for shipping in process step 4.

Following this, in step 5, the whole tobacco plant is conditioned by using steam, water or a mixture thereof, in order to reach a predetermined moisture degree in the oriental tobacco plant material to provide a conditioned plant in having greater than 18% O.V (oven volatiles).

Once the desired moisture content is reached, the whole tobacco plant is prepared for threshing in process step 6. During the threshing process, the whole tobacco plant is threshed by standard threshing machines, in order to separate the leaf material from the stalk and stem material.

Once the leaf material has been separated from the stalk and stem material of the whole oriental tobacco plant, the leaf material then undergoes a further drying process in step 7. In this step, the leaf material is dried by a hot air stream, in order to reach a predetermined moisture degree that is low enough to allow for easier cutting and storage. This is typically below 12% O.V.

Once the oriental leaf material reaches the predetermined moisture degree through the drying process, the leaf material is then cut in step 8. The leaf is typically cut to a width of about 0.8 to 0.9 mm, in order be ready for use in a smoking article, such as a cigarette. 

1. A method of processing oriental sun-cured tobacco, comprising: harvesting a predetermined amount of whole oriental tobacco plants, and curing the leaves on the whole oriental tobacco plants by exposing them to sunlight, without separating the leaves from the stalk.
 2. The method according to claim 1 wherein the whole tobacco plants are attached to or supported on a support material.
 3. The method according to claim 2 wherein the support material is a string, wire, rod, pole, stick or similar elongate material upon which the whole tobacco plant can be attached.
 4. The method according to claim 2 wherein the whole tobacco plants are attached to the support material at or through the stalk end of the plant and are hung upside-down on the support material.
 5. The method according to claim 2 wherein dividers are provided on the support material between the whole tobacco plants.
 6. The method according to claim 2 wherein the leaves of the cured whole tobacco plants are removed from the rest of the plants whilst plants are still attached to or supported by the support material.
 7. The method according to claim 1 wherein the cured whole tobacco plants are stored under a cover that is open to the atmosphere.
 8. The method according to claim 1 wherein the cured whole tobacco plants are threshed in a leaf processing facility, in order to separate leaf from stalk material.
 9. The method according to claim 1 wherein the leaves of the tobacco plants are further cut to a width of between 0.3 to 1.3 mm, in order to create cut leaf ready for use in a smoking article.
 10. The method according to claim 3 wherein the whole tobacco plants are attached to the support material at or through the stalk end of the plant and are hung upside-down on the support material.
 11. The method according to claim 2 further comprising the curing the supported whole tobacco plants to form a cured whole tobacco plant.
 12. The method according to claim 11 wherein the curing comprises exposing the whole tobacco plants to sunlight for a period of about ten to twenty days.
 13. The method according to claim 11 further comprising bailing the cured whole tobacco plant to form a bail of cured whole tobacco plants.
 14. The method according to claim 13 further comprising conditioning the bail of cured whole tobacco plants, wherein the conditioning comprises steam or water to provide a conditioned cured whole tobacco plant material having greater than 18% O.V.
 15. The method according to claim 14 further comprising threshing the conditioned cured whole tobacco plant material to separate the leaf material from the stalk and stem material.
 16. The method according to claim 15 further comprising drying the leaf material to form a dried leaf material.
 17. The method according to claim 16 wherein the drying comprises drying the leaf material to a predetermined moisture level below 12% O.V.
 18. The method according to claim 16 further comprising cutting the dried leaf material to a width of between 0.3 to 1.3 mm, in order to create cut leaf ready for use in a smoking article.
 19. The method according to claim 16 further comprising cutting the dried leaf material to a width of between 0.8 to 0.9 mm, in order to create cut leaf ready for use in a smoking article.
 20. The method according to claim 11 further comprising separating the tobacco leaves from the stalk of the cured whole tobacco plant. 